Proximity Sensors and Android Classes
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Questions and Answers

What is the primary function of a proximity sensor?

  • To determine the distance of an object from the device (correct)
  • To detect changes in sensor accuracy
  • To provide sensor event data when triggered
  • To measure magnetic field strength along the axes

    • Which class provides information about a specific sensor and its characteristics?

  • Sensor (correct)
  • SensorManager
  • SensorEventListener
  • SensorEvent

    • What does the SensorEvent class contain when an event occurs?

  • Sensor generating the event and timestamp (correct)
  • Sensor accuracy only
  • Sensor name and listener interface
  • Sensor type and range only

    • What is the role of the SensorManager class?

    <p>To register and unregister sensor event listeners (D)</p> Signup and view all the answers

    Which method in the SensorEventListener interface is triggered when new sensor data is available?

    <p>onSensorChanged (D)</p> Signup and view all the answers

    What action does the ACTION_DOWN case log in the touch event listener?

    <p>Starting coordinates of the touch. (A)</p> Signup and view all the answers

    Which sensor measures acceleration applied to the device along the x, y, and z axes?

    <p>Accelerometer (D)</p> Signup and view all the answers

    What does the ACTION_MOVE case do in the touch event listener?

    <p>Logs coordinates as the finger moves. (D)</p> Signup and view all the answers

    Which of the following sensors measures atmospheric pressure?

    <p>Pressure Sensor (C)</p> Signup and view all the answers

    When a touch event is released, which case is triggered to log the coordinates?

    <p>ACTION_UP (C)</p> Signup and view all the answers

    What type of sensor measures ambient light level in lux?

    <p>Light Sensor (C)</p> Signup and view all the answers

    What does the ACTION_UP case log in the touch event listener?

    <p>Final coordinates when the touch is released. (D)</p> Signup and view all the answers

    Which of the following corresponds with a Motion Sensor?

    <p>Measures the rate of rotation around the device's axes. (B)</p> Signup and view all the answers

    What is required for a dangerous permission in an application?

    <p>User approval needed (D)</p> Signup and view all the answers

    Which of the following is classified as a normal permission?

    <p>ACCESS_NETWORK_STATE (C)</p> Signup and view all the answers

    What type of storage method is NOT typically used for saving data locally in an app?

    <p>Firebase cloud storage (B)</p> Signup and view all the answers

    Which storage solution allows for data sharing between applications?

    <p>Content Providers (D)</p> Signup and view all the answers

    What is the function of a ContentProvider in Android applications?

    <p>To enable secure data sharing between apps (D)</p> Signup and view all the answers

    Which method allows data to be stored and accessed only within the app?

    <p>Local bundles (C)</p> Signup and view all the answers

    What must be considered when choosing a data-saving method?

    <p>Whether the storage is local or remote (A)</p> Signup and view all the answers

    What defines whether data is accessible between apps?

    <p>The storage method used (A)</p> Signup and view all the answers

    What is the primary method to temporarily store data during an application's instance?

    <p>Bundle (B)</p> Signup and view all the answers

    Which method is called to save instance state in an activity?

    <p>onSaveInstanceState() (C)</p> Signup and view all the answers

    In which lifecycle method should preferences generally be stored?

    <p>onPause() (D)</p> Signup and view all the answers

    What is the correct way to retrieve data saved in a Bundle during onCreate()?

    <p>savedInstanceState.getString(key) (B)</p> Signup and view all the answers

    What should be checked before restoring data from a Bundle in onCreate()?

    <p>If savedInstanceState is not null (A)</p> Signup and view all the answers

    Which statement about SharedPreferences is true?

    <p>Preferences can be shared across multiple activities. (A)</p> Signup and view all the answers

    How is data put into a Bundle during onSaveInstanceState?

    <p>Using putString(key, value) (D)</p> Signup and view all the answers

    When is onPause() called in relation to onCreate()?

    <p>After onCreate() (C)</p> Signup and view all the answers

    What is one of the main advantages of using ContentProviders for app data management?

    <p>They facilitate cross-app communication with controlled access. (A)</p> Signup and view all the answers

    Which of the following is NOT a key feature of ContentProviders?

    <p>Automatic Data Encryption (C)</p> Signup and view all the answers

    What type of data is most appropriate for storage using SharedPreferences?

    <p>User preferences and settings (C)</p> Signup and view all the answers

    How do ContentProviders facilitate data updates for applications that access them?

    <p>Through cursor-based querying and observer notifications. (C)</p> Signup and view all the answers

    Which built-in ContentProvider allows access to user contacts?

    <p>ContactsProvider (A)</p> Signup and view all the answers

    What storage method is best suited for structured and scalable data needs in an app?

    <p>SQLite and Room Database (D)</p> Signup and view all the answers

    What does the concept of 'data abstraction' refer to in the context of ContentProviders?

    <p>Apps can work with data without knowing the storage mechanism. (B)</p> Signup and view all the answers

    Which type of storage is temporary and ideal for passing data between activities during screen rotations?

    <p>Bundles (C)</p> Signup and view all the answers

    What method must be called to ensure preferences are stored properly during OnPause()?

    <p>super.onPause() (D)</p> Signup and view all the answers

    What is the purpose of using SharedPreferences in an application?

    <p>Persist user preferences across app sessions (C)</p> Signup and view all the answers

    Which method is used to read a stored string from SharedPreferences?

    <p>preferences.getString() (D)</p> Signup and view all the answers

    What is the difference between getPreferences() and getSharedPreferences()?

    <p>getPreferences() does not take a name parameter (C)</p> Signup and view all the answers

    Which of the following should be used to commit changes to SharedPreferences after editing?

    <p>editor.commit() (A), editor.apply() (B)</p> Signup and view all the answers

    What type of data is best suited to be managed by SharedPreferences?

    <p>User preferences that should persist across sessions (D)</p> Signup and view all the answers

    What default value is used when retrieving a string from SharedPreferences if the key does not exist?

    <p>&quot;&quot; (empty string) (D)</p> Signup and view all the answers

    What is a key characteristic of data stored using SharedPreferences compared to Bundle?

    <p>SharedPreferences data is permanent across app sessions. (A)</p> Signup and view all the answers

    Flashcards

    ACTION_DOWN in Touch Event

    The MotionEvent.ACTION_DOWN action signals the beginning of a touch event. It records the initial touch coordinates (x,y) on the device's screen.

    ACTION_MOVE in Touch Event

    The MotionEvent.ACTION_MOVE action tracks the touch as it moves across the screen. It continually records the touch coordinates (x,y) as the finger moves.

    ACTION_UP in Touch Event

    The MotionEvent.ACTION_UP action marks the end of the touch event, recording the final touch coordinates (x,y) on the screen.

    Accelerometer

    A sensor type used to measure acceleration forces applied to the device along its three axes (x, y, and z)

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    Gyroscope

    A sensor type used to measure the rate of rotation around the device's three axes (x, y, and z)

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    Light Sensor

    A sensor type used to measure the level of ambient light in lux (a unit of illuminance)

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    Temperature Sensor

    A sensor type used to measure the ambient air temperature around the device

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    Pressure Sensor

    A sensor type used to measure air pressure, typically utilized for altitude measurements

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    Proximity Sensor

    A type of sensor that determines the distance of an object from the device It detects the presence of nearby objects without physical contact.

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    Magnetic Field Sensor

    A type of sensor that measures the strength of a magnetic field along three axes (x, y, z).

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    SensorManager

    A framework class in Android that provides access to device sensors. It allows you to register and unregister sensor event listeners. It also provides constants for sensor accuracy and data acquisition rates.

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    Sensor

    A framework class in Android that represents a specific sensor and its characteristics. It provides information about the sensor's name, type, range, resolution, and power consumption.

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    SensorEvent

    A framework class in Android that provides data from sensors when an event occurs. It contains information about the sensor generating the event, the captured data, the accuracy of the data, and the timestamp of the event.

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    Dangerous Permissions

    Permissions that require explicit user approval before being granted to an app.

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    Normal Permissions

    Permissions that are automatically granted to an app when installed.

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    Local Storage

    Storing data on the user's device. This data is only accessible by the app itself and requires no internet connection.

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    Remote Storage

    Storing data on a remote server, accessible from anywhere with an internet connection.

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    Content Providers

    A storage method that allows sharing data between different Android applications.

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    SharedPreferences

    A lightweight storage method for storing simple key-value pairs.

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    SQLite

    A powerful database system for storing structured data on a local device.

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    What is a ContentProvider?

    A mechanism allowing different Android apps to access, modify, and delete data in another application.

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    How do ContentProviders ensure data security?

    ContentProviders enforce security rules, allowing you to control who can access what data.

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    What is data abstraction in ContentProviders?

    ContentProviders abstract the underlying data storage method, meaning apps don't need to know how data is stored (e.g., SQLite, files).

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    What is a URI in the context of ContentProviders?

    A standard web-like address used to access specific data resources within a ContentProvider.

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    What are access permissions in ContentProviders?

    They grant or deny read or write permissions for specific sections of your app's data.

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    How do ContentProviders interact with datasets?

    ContentProviders utilize cursors to efficiently manage and navigate large datasets.

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    How do ContentProviders keep apps informed about data changes?

    ContentProviders notify apps whenever data changes, enabling dynamic updates.

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    What are examples of pre-built ContentProviders in Android?

    Android provides built-in ContentProviders for accessing common system-level data.

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    onSaveInstanceState() and Bundle

    A temporary storage mechanism within an Android application instance, allowing data to be saved and restored when the application is interrupted or restarted. It's primarily used for retaining UI state or temporary data that doesn't require permanent storage.

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    Bundle

    A specialized data structure used by Android to pass information between application components, such as activities or fragments.

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    onSaveInstanceState()

    A method called by the Android system to save data associated with an activity before it's destroyed or paused. This allows the activity to restore its state when it's recreated later.

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    onCreate(Bundle)

    A method called by the Android system to restore the saved state of an activity when it's recreated after being destroyed or paused.

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    onPause()

    A method called by the Android system when an activity is about to be sent to the background. This is a suitable time to save data to SharedPreferences as the application will be inactive for a while.

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    onCreate()

    A method called by the Android system when an activity is created or restarted. You can restore saved data from SharedPreferences here, allowing the activity to start with its previous state.

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    Application preferences (SharedPreferences)

    Preferences that are saved for the entire application and are accessible to all activities within the app.

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    Activity preferences (SharedPreferences)

    Preferences that are tied to a specific activity and only available within that activity.

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    getPrefs()

    A function that retrieves and sets the value of a key-value pair.

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    SharedPreferences Editor ('edit()')

    A method used to save preferences and requires a call to either 'commit()' or 'apply()' to save the values to memory.

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    SharedPreferences.Editor.commit() or apply()

    A function that saves edited preference values to memory.

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    preferences.getString("key", "")

    A method used to retrieve a specific value from the SharedPreferences.

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    Study Notes

    Input Systems in Android

    • Android input systems utilize various methods like keyboards, touchscreens, controllers, and sensors.
    • The View class is central to input management, acting as the user interface component that listens for and handles input events.
    • Listeners provide a structured approach to handle user actions, enabling responsive app design.

    Keyboard Input

    • View.OnKeyListener is an Android interface designed for listening to keyboard events within a specific View.
    • It detects key presses (down, released, and typed).
    • The primary method is boolean onKey(View v, int keyCode, KeyEvent event).
    • KeyEvent.KEYCODE_* constants represent specific keys on the device.
    • Example constants include alphanumeric keys, functional keys (like Enter or Delete), and special keys (like volume controls or the camera button).

    Touch Input

    • OnTouchListener is an interface for listening to touch events on a View.
    • It enables detection and response to touch interactions, such as pressing, releasing, and moving a finger on a View.
    • The primary method is boolean onTouch(View v, MotionEvent event).
    • The MotionEvent class contains comprehensive data on touch events, including coordinates and action types.
    • Common actions include ACTION_DOWN, ACTION_MOVE, and ACTION_UP.

    Android Sensors

    • Android devices incorporate various sensors that measure physical forces and environmental parameters.

    • Motion sensors measure acceleration and rotational forces, encompassing:

    • Accelerometer: Measures acceleration along the x, y, and z axes.

    • Gyroscope: Measures rotational speed around the x, y, and z axes.

    • Environmental sensors measure various parameters like:

    • Light Sensor: Measures ambient light level

    • Temperature sensor: Measures ambient air temperature

    • Pressure Sensor: Measures atmospheric pressure

    • Position Sensors: Measure physical position or proximity to other objects, including proximity sensors and Magnetic Field sensors

    Framework Classes for Sensors

    • SensorManager: Manages access to device sensors, registers/unregisters event listeners, and provides constants for accuracy and data acquisition rates.
    • Sensor: Represents a specific sensor and its properties, including sensor type, range, resolution, and power requirements.
    • SensorEvent: Holds data from sensors during events, including sensor type, values, accuracy, and timestamp.
    • SensorEventListener: An interface for receiving sensor event notifications (e.g., accuracy changes, new sensor data).

    Handling Sensor Data

    • Example handling of accelerometers or other sensor data via onSensorChanged method.

    Permissions

    • Permissions are essential for granting access to specific device features.
    • Dangerous Permissions: Require explicit user approval to avoid malicious access, including access to contacts, location, or microphone.
    • Normal Permissions: Are automatically granted at installation, enabling less sensitive access like network access.

    Saving Data

    • Applications can store data in various ways, depending on whether it's temporary (during the app session) or permanent (across sessions).
    • Temporary data: stored in bundles and used for short-lived data like screen rotations.
    • Permanent Data: Stored using SharedPreferences (small amounts of data, frequently updated data) or SQLite (structured and relatively large datasets).

    Dynamic Data

    • Dynamic data is data that changes frequently.
    • Data objects can be notified of changes using observers.
    • Applications can use techniques such as super.onResume, or super.onPause() to handle changes in dynamic data appropriately

    Screen Rotation

    • Screen rotation triggers several activity events: onPause(), onStop(), onDestroy(), onCreate(), onStart(), and onResume().
    • Data must be handled during these events to maintain application functionality throughout rotation.

    Data Storage Methods

    • Bundles: Suitable for temporary data (e.g., data across activities, screen rotation)
    • SharedPreferences: Used for storing simple, frequently accessed data (e.g., user preferences)
    • SQLite and Room: Designed for structured, persistent data (e.g., user data, app state).

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    Related Documents

    Android Input Systems (PDF)

    Description

    Test your knowledge on proximity sensors and Android sensor classes with this quiz. It covers various aspects like SensorEvent, SensorManager, and touch event listeners. Ideal for students and professionals interested in Android development.

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